You have a lot of bench spots being taken up by hitters so i would be fine dropping Aviles for Oswalt. I don't love it but no reason to keep him if you are just benching him and I don't see much playing time for him. Only other option is to do a 2-1 and then pick up Oswalt.

"In the beginning the Universe was created. This has made a lot of people very angry and has been widely regarded as a bad move."- Douglas Adams

I would stay with what you have. Your pitching is pretty good without him. I would keep Aviles because of his position flexibilty if someone gets hurt. Aviles would be the one to drop for Oswalt if you are going to do it.